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The moose (pl.: 'moose'; used in North America) or elk (pl.: 'elk' or 'elks'; used in Eurasia) (Alces alces) is the world's tallest, largest and heaviest extant species of deer and the only species in the genus Alces. It is also the tallest, and the second-largest, land animal in North America, falling short only to the American bison in body mass. Most adult male moose have broad, palmate ("open-hand shaped") antlers; other members of the deer family have pointed antlers with a dendritic ("twig-like") configuration. Moose inhabit the circumpolar boreal forests or temperate broadleaf and mixed forests of the Northern Hemisphere, thriving in cooler, temperate areas as well as subarctic climates.
Hunting shaped the relationship between moose and humans, both in Eurasia and North America. Prior to the early modern period (around 1600–1700), moose were one of many valuable sources of sustenance for certain North American Indians. Hunting and habitat loss have reduced the moose's range; this fragmentation has led to sightings of "urban moose" in some areas. The moose has been reintroduced to some of its former habitats. Currently, the greatest populations occur in Canada. Additionally, substantial numbers are found in Alaska, the northern states of the contiguous United States, Fennoscandia, the Baltic states, the Caucasus region, Poland, Eastern Europe, Mongolia, Kazakhstan, and Russia.
Predominantly a browser, the moose's diet consists of both terrestrial and aquatic vegetation, depending on the season, with branches, twigs and dead wood making up a large portion of their winter diet. Predators of moose include wolves, bears, humans, wolverines (rarely, though may take calves), and (rarely, if swimming in the ocean) orcas. Unlike most other deer species, moose do not form herds and are solitary animals, aside from calves who remain with their mother until the cow begins estrus again (typically 18 months after the birth of a calf). At this point, the cow chases her calf away. Although generally slow-moving and sedentary, moose can become defensively aggressive, and move very quickly if angered or startled. Their mating season in the autumn features energetic fights between males competing for a female.
Moose have played a prominent role in the culture of people in the Northern Hemisphere. Evidence suggests they were hunted by humans as far back as the most recent Ice Age.[3]
Taxonomy
Etymology
Alces alces is called a "moose" in North American English, but an "elk" in British English.[4] The word "elk" in North American English refers to a completely different species of deer, Cervus canadensis, also called the wapiti (from Algonquin). A mature male moose is called a bull, a mature female a cow, and an immature moose of either sex a calf.
In Classical Antiquity, the animal was known as ἄλκη (álkē)[5] in Greek and alces[6] in Latin, words probably borrowed from a Germanic language or another language of northern Europe.[4] By the 8th century, during the Early Middle Ages, the species was known in Old English: elch, elh, eolh, derived from the Proto-Germanic: *elho-, *elhon- and possibly connected with the Old Norse: elgr.[4] Later, in Middle English, the species became known as elk, elcke, or elke, also appearing in the Latinized form alke, with the alce borrowed directly from the Latin: alces.[4][7]
The word "elk" remained in usage because of English-speakers' familiarity with the species in Continental Europe; however, without any living animals around to serve as a reference, the meaning became rather vague, and by the 17th century "elk" had a meaning similar to "large deer".[8] Dictionaries of the 18th century simply described "elk" as a deer that was "as large as a horse".[9]
The word "moose" had first entered English by 1606[10] and is borrowed from the Algonquian languages (compare the Narragansett moos and Eastern Abenaki mos; according to early sources, these were likely derived from moosu, meaning 'he strips off'),[11] and possibly involved forms from multiple languages mutually reinforcing one another. The Proto-Algonquian form was *mo·swa.[12]
Description
On average, an adult moose stands 1.4–2.1 m (4 ft 7 in – 6 ft 11 in) high at the shoulder, which is more than 30 centimetres (1 ft) higher than the next-largest deer on average, the wapiti.[13] The tail is short (6 cm to 8 cm in length) and vestigial in appearance; unlike other ungulates the moose tail is too short to swish away insects.[14] Males (or "bulls") normally weigh from 380 to 700 kg (838 to 1,543 lb) and females (or "cows") typically weigh 200 to 490 kg (441 to 1,080 lb), depending on racial or clinal as well as individual age or nutritional variations.[15][16] The head-and-body length is 2.4–3.1 m (7 ft 10 in – 10 ft 2 in), with the vestigial tail adding only a further 5–12 cm (2–41⁄2 in).[17] The largest of all the races is the Alaskan subspecies (A. a. gigas), which can stand over 2.1 m (6 ft 11 in) at the shoulder, has a span across the antlers of 1.8 m (5 ft 11 in) and averages 634.5 kg (1,399 lb) in males and 478 kg (1,054 lb) in females.[18] Typically, however, the antlers of a mature bull are between 1.2 and 1.5 m (3 ft 11 in and 4 ft 11 in). The largest confirmed size for this species was a bull shot at the Yukon River in September 1897 that weighed 820 kg (1,808 lb) and measured 2.33 m (7 ft 8 in) high at the shoulder.[19] There have been reported cases of even larger moose, including a bull killed in 2004 that weighed 1,043 kg (2,299 lb),[20] and a bull that reportedly scaled 1,180 kg (2,601 lb), but none are authenticated and some may not be considered reliable.[19]
Antlers
Bull moose have antlers like other members of the deer family. The size and growth rate of antlers is determined by diet and age.[21] Size and symmetry in the number of antler points signals bull moose health and cows may select mates based on antler size and symmetry.[22] Bull moose use their antlers to display dominance, to discourage competition, and to spar or fight rivals.[21]
The male's antlers grow as cylindrical beams projecting on each side of the head at right angles to the midline of the skull, and then fork. The lower prong of this fork may be either simple, or divided into two or three tines, with some flattening. Most moose have antlers that are broad and palmate (flat) with tines (points) along the outer edge.[21] Within the ecologic range of the moose in Europe, northern populations display the palmate pattern of antlers, while the antlers of European moose residing the southerly portion of its range are typically of the cervina dendritic pattern and comparatively small, perhaps due to evolutionary pressures of hunting by humans, who prize the large palmate antlers. European moose with antlers intermediate between the palmate and the dendritic form are found in the middle of the north-south range.[23] Moose with antlers have more acute hearing than those without antlers; a study of trophy antlers using a microphone found that the palmate antler acts as a parabolic reflector, amplifying sound at the moose's ear.[24]
The antlers of mature Alaskan adult bull moose (5 to 12 years old) have a maximum spread greater than 200 centimeters (79 in). By the age of 13, moose antlers decline in size and symmetry. The widest spread recorded was 210 centimeters (83 in) across. An Alaskan moose also holds the record for the heaviest weight at 36 kilograms (79 lb).[21]
Antler beam diameter, not the number of tines, indicates age.[21] In North America, moose (A. a. americanus) antlers are usually larger than those of Eurasian moose and have two lobes on each side, like a butterfly. Eurasian moose antlers resemble a seashell, with a single lobe on each side.[21] In the North Siberian moose (A. a. bedfordiae), the posterior division of the main fork divides into three tines, with no distinct flattening. In the common moose (A. a. alces) this branch usually expands into a broad palmation, with one large tine at the base and a number of smaller snags on the free border. There is, however, a Scandinavian breed of the common moose in which the antlers are simpler and recall those of the East Siberian animals. The palmation appears to be more marked in North American moose than in the typical Scandinavian moose.
After the mating season males drop their antlers to conserve energy for the winter. A new set of antlers will then regrow in the spring. Antlers take three to five months to fully develop, making them one of the fastest growing animal organs. Antler growth is "nourished by an extensive system of blood vessels in the skin covering, which contains numerous hair follicles that give it a 'velvet' texture."[21] This requires intense grazing on a highly-nutritious diet. By September the velvet is removed by rubbing and thrashing which changes the colour of the antlers. Immature bulls may not shed their antlers for the winter, but retain them until the following spring. Birds, carnivores and rodents eat dropped antlers as they are full of protein and moose themselves will eat antler velvet for the nutrients.[21]
If a bull moose is castrated, either by accidental or chemical means, he will shed his current set of antlers within two weeks and then immediately begin to grow a new set of misshapen and deformed antlers that he will wear the rest of his life without ever shedding again; similarly deformed antlers can result from a deficiency of testosterone caused by cryptorchidism or old age.[25] These deformed antlers are composed of living bone which is still growing or able to grow, since testosterone is needed to stop antler growth;[26] they may take one of two forms. "Cactus antlers" or velericorn antlers[26] usually retain the approximate shape of a normal moose's antlers but have numerous pearl-shaped exostoses on their surface; being made of living bone, they are easily broken but can grow back. Perukes (US: /pəˈruːks/) are constantly growing, tumor-like antlers with a distinctive appearance similar to coral.[25] Like roe deer, moose are more likely to develop perukes, rather than cactus antlers, than the more developed cervine deer, but unlike roe deer, moose do not suffer fatal decalcification of the skull as a result of peruke growth,[27][26] but rather can support their continued growth until they become too large to be fully supplied with blood.[25] The distinctive-looking perukes (often referred to as "devil's antlers") are the source of several myths and legends among many groups of Inuit as well as several other tribes of indigenous peoples of North America.
In extremely rare circumstances, a cow moose may grow antlers. This is usually attributed to a hormone imbalance.[28]
Proboscis and olfaction
The moose proboscis is distinctive among living cervids due to its large size; it also features nares that can be sealed shut when the moose is browsing aquatic vegetation. The moose proboscis likely evolved as an adaptation to aquatic browsing, with loss of the rhinarium, and development of a superior olfactory column separate from an inferior respiratory column.[29] This separation contributes to the moose's keen sense of smell, which they employ to detect water sources, to find food under snow, and to detect mates or predators.[30][29]
Hooves
As with all members of the order Artiodactyla (even-toed ungulates), moose feet have two large keratinized hooves corresponding to the third and fourth toe, with two small posterolateral dewclaws (vestigial digits), corresponding to the second and fifth toe. The hoof of the fourth digit is broader than that of the third digit, while the inner hoof of the third digit is longer than that of the fourth digit. This foot configuration may favor striding on soft ground.[31] The moose hoof splays under load, increasing surface area, which limits sinking of the moose foot into soft ground or snow, and which increases efficiency when swimming. The body weight per footprint surface area of the moose foot is intermediate between that of the pronghorn foot, (which have stiff feet lacking dewclaws—optimized for high-speed running) and the caribou foot (which are more rounded with large dewclaws, optimized for walking in deep snow). The moose's body weight per surface area of footprint is about twice that of the caribou.[32][33]
Skin and fur
Moose skin is typical of the deer family. Moose fur consists of four types of hair: eyelashes, whiskers, guard hairs and wool hairs. Hair length and hair density varies according to season, age, and body region.[34] The coat has two layers—a top layer of long guard hairs and a soft wooly undercoat. The guard hairs are hollow and filled with air for better insulation, which also helps them stay afloat when swimming.[35][36]
Dewlap
Both male and female moose have a dewlap or bell,[37] which is a fold of skin under the chin. Its exact function is unknown, but some morphologic analyses suggest a cooling (thermoregulatory) function.[38] Other theories include a fitness signal in mating, as a visual and olfactory signal, or as a dominance signal by males, as are the antlers.[39]
Ecology and biology
Diet
The moose is a browsing herbivore and is capable of consuming many types of plant or fruit. The average adult moose needs to consume 96 megajoules (23,000 kilocalories) per day to maintain its body weight.[40] Much of a moose's energy is derived from terrestrial vegetation, mainly consisting of forbs and other non-grasses, and fresh shoots from trees such as willow and birch. As these terrestrial plants are rather low in sodium, as much as half of its diet usually consists of aquatic plants, including lilies and pondweed,[41] which while lower in energy content, provide the moose with its sodium requirements.[42] In winter, moose are often drawn to roadways, to lick salt that is used as a snow and ice melter.[43] A typical moose, weighing 360 kg (794 lb), can eat up to 32 kg (71 lb) of food per day.[42]
Moose lack upper front teeth, but have eight sharp incisors on the lower jaw. They also have a tough tongue, lips and gums, which aid in the eating of woody vegetation. Moose have six pairs of large, flat molars and, ahead of those, six pairs of premolars, to grind up their food. A moose's upper lip is very sensitive, to help distinguish between fresh shoots and harder twigs, and is prehensile, for grasping their food. In the summer, moose may use this prehensile lip for grabbing branches and pulling, stripping the entire branch of leaves in a single mouthful, or for pulling forbs, like dandelions, or aquatic plants up by the base, roots and all.[44][45] A moose's diet often depends on its location, but they seem to prefer the new growths from deciduous trees with a high sugar content, such as white birch, trembling aspen and striped maple, among many others.[46] To reach high branches, a moose may bend small saplings down, using its prehensile lip, mouth or body. For larger trees a moose may stand erect and walk upright on its hind legs, allowing it to reach branches up to 4.26 meters (14 ft 0 in) or higher above the ground.[47][48] Moose may consume ferns from time to time.[49]
Moose are excellent swimmers and are known to wade into water to eat aquatic plants. This trait serves a second purpose in cooling down the moose on summer days and ridding itself of black flies. Moose are thus attracted to marshes and river banks during warmer months as both provide suitable vegetation to eat and water to wet themselves in. Moose have been known to dive over 5.5 metres (18 ft) to reach plants on lake bottoms,[50] and the complex snout may assist the moose in this type of feeding. Moose are the only deer that are capable of feeding underwater.[51] As an adaptation for feeding on plants underwater, the nose is equipped with fatty pads and muscles that close the nostrils when exposed to water pressure, preventing water from entering the nose.[52] Other species can pluck plants from the water too, but these need to raise their heads in order to swallow.
Moose are not grazing animals but browsers (concentrate selectors), and their diet varies on a continuum between soft-leaf browsing and browsing of lignified plant matter.[53] Like giraffes, moose carefully select foods with less fiber and more concentrations of nutrients. Thus, the moose's digestive system has evolved to accommodate this relatively low-fiber diet. Unlike most hooved, domesticated animals (ruminants), moose cannot digest hay, and feeding it to a moose can be fatal.[54][55] The moose's varied and complex diet is typically expensive for humans to provide, and free-range moose require a lot of forested hectarage for sustainable survival, which is one of the main reasons moose have never been widely domesticated.[citation needed]
Natural predators
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A full-grown moose has few enemies except Siberian tigers (Panthera tigris tigris) which regularly prey on adult moose,[56][57][58] but a pack of gray wolves (Canis lupus) can still pose a threat, especially to females with calves.[59] Brown bears (Ursus arctos)[18] are also known to prey on moose of various sizes and are the only predator besides the wolf to attack moose both in Eurasia and North America. In Western Russia, moose provide about 15% annual estimated dietary energy content for brown bears and are the most important food source for these predators during spring.[60] However, Brown bears are more likely to scavenge a wolf kill or to take young moose than to hunt adult moose on their own.[61][62][63] Black bears (Ursus americanus) and cougars (Puma concolor) can be significant predators of moose calves in May and June and can, in rare instances, prey on adults (mainly cows rather than the larger bulls).[64][65] Wolverines (Gulo gulo) are most likely to eat moose as carrion but have killed moose, including adults, when the large ungulates are weakened by harsh winter conditions.[66][67][68] Orcas (Orcinus orca) are the moose's only confirmed marine predator as they have been known to prey on moose and other deer swimming between islands out of North America's Northwest Coast. However, such kills are rare and a matter of opportunity, as moose are not a regular part of the orca diet.[69] There is at least one recorded instance of a moose being scavenged by a Greenland shark (Somniosus microcephalus).[70]
In some areas, moose are the primary source of food for wolves. Moose usually flee upon detecting wolves. Wolves usually follow moose at a distance of 100 to 400 meters (300 to 1,300 ft), occasionally at a distance of two to three kilometers (1 to 2 mi). Attacks from wolves against young moose may last seconds, though sometimes they can be drawn out for days with adults. Sometimes, wolves will chase moose into shallow streams or onto frozen rivers, where their mobility is greatly impeded. Moose will sometimes stand their ground and defend themselves by charging at the wolves or lashing out at them with their powerful hooves. Wolves typically kill moose by tearing at their haunches and perineum, causing massive blood loss. Occasionally, a wolf may immobilize a moose by biting its sensitive nose, the pain of which can paralyze a moose.[71] Wolf packs primarily target calves and elderly animals, but can and will take healthy, adult moose. Moose between the ages of two and eight are seldom killed by wolves.[72] Though moose are usually hunted by packs, there are cases in which single wolves have successfully killed healthy, fully-grown moose.[73][74]
Research into moose predation suggests that their response to perceived threats is learned rather than instinctual. In practical terms this means moose are more vulnerable in areas where wolf or bear populations were decimated in the past but are now rebounding. These same studies suggest, however, that moose learn quickly and adapt, fleeing an area if they hear or smell wolves, bears, or scavenger birds such as ravens.[75]
Moose are also subject to various diseases and forms of parasitism. In northern Europe, the moose botfly is a parasite whose range seems to be spreading.